i experience this on my X it will stop charging when i play games even for a little bit.not using a wireless charging just the 5w(included)but i notice it often when i use my ipad charger.its usually stop charging above 75%.the only way you can tell is when you download the app lirum info and go to tools then battery you can see it on the screenshot below but right now is charging ok because i only use it on the browser.it always show in the notification area that its charging but its really not